CN105790579B

CN105790579B - Power converter controller

Info

Publication number: CN105790579B
Application number: CN201610128206.1A
Authority: CN
Inventors: 霍斯特·克内德根; 朱利安·泰瑞尔
Original assignee: Dialog Semiconductor UK Ltd
Current assignee: Dialog; Dialog Semiconductor UK Ltd
Priority date: 2015-12-01
Filing date: 2016-03-07
Publication date: 2020-06-12
Anticipated expiration: 2036-03-07
Also published as: DE102015223920A1; CN105790579A; US10334667B2; US20170156184A1; DE102015223920B4

Abstract

The present application relates to a controller for a power converter for converting electrical power at an input voltage to electrical power at an output voltage, and a method of operating the controller. The controller for controlling the power converter includes an input port for receiving a voltage representative of an input voltage; an input voltage measurement unit for sampling a measured voltage and determining a measured value representative of the input voltage; a switch; and a diode connectable to the memory cell to provide a voltage supply to the controller during operation of the controller, wherein the switch is controlled to control charging of the memory cell from the voltage at the input port.

Description

Power converter controller

Technical Field

The present invention relates to mains measurement and power supply charging mode for power converters, in particular for LED drivers.

Background

The supply voltage of mains-supplied LED drivers is usually generated by an external supply, or a third winding on the flyback switching coil. When the device is turned on for the first time, the usual approach is to initially charge the VCC supply from the input voltage sense resistor-through the internal diode-and then turn on the internal resistor to form a voltage divider, thereby achieving the rail voltage measurement. Other alternative techniques employ external zener diodes and bleed resistors and power from the third winding. In any way, the power supply of such a driver IC requires the use of a large number of external components.

Therefore, there is a need to provide a more efficient power converter for power conversion such as LED drivers, in particular a controller IC that controls the operation of the power converter, e.g. by driving one or more switches of a switched mode power converter. It would be beneficial if the power converter could reuse existing means for measuring the input voltage of the power converter, for example a rectified AC (alternating current) input as provided by mains supply, thereby reducing the pin count of the controller IC. Preferably, the number of external components is reduced to achieve a cost-effective solution.

Disclosure of Invention

In light of this need, a controller for controlling a power converter and a method of powering a controller of a power converter are presented herein, the controller and the method having the features of the respective independent claims.

According to an aspect of the present invention, there is provided a controller for controlling a power converter to convert electric power at an input voltage to electric power at an output voltage. The controller includes an input port for receiving a voltage representative of, e.g., derived from, the input voltage such that the input voltage may be determined by receiving the voltage. The controller further comprises an input voltage measurement unit for sampling the measured voltage at the point in time of measurement and determining a measured value representing the input voltage. In other words, the input voltage measurement unit may determine the input voltage by sampling the measured voltage, which may be the voltage received at the input port or a voltage derived from the input port. The controller also includes a diode connectable with the memory cell to provide a supply voltage to the controller during operation of the controller. The storage unit may be a charge storage unit such as a capacitor, in particular an external capacitor connected to the controller via the VCC port. Thus, when properly charged, the capacitor provides the supply voltage VCC for operating the controller.

Furthermore, a switch is provided which can be controlled to be opened or closed, i.e. set to a non-conductive or conductive state. The switch is connectable between the input port and the input voltage measuring unit and, when closed, connects the input voltage measuring unit to the input port so that the voltage at the input port can be sampled and measured. However, in some embodiments, other configurations are possible, as explained below. The input voltage measuring unit may be an analog-to-digital converter (ADC) that samples and measures the measured voltage at a measurement time point based on a received control signal when triggered. The switch may be controlled based on a further control signal to control the input port voltage to charge the storage unit, thereby ensuring that the storage unit may provide the necessary supply voltage for operating the controller. For example, the storage capacitor is charged through a diode when the switch is open, and the capacitor is not charged when the switch is closed. The storage capacitor can provide a supply voltage regardless of the switch state, i.e. when the switch is open and closed.

The above circuit configuration allows the memory cell to be charged and the input voltage measured through a single pin of the controller. Furthermore, no other means of charging the storage unit, such as an output voltage from a controller like the third winding of the flyback switching coil, is required. In other words, the memory cell is only charged through the input port of the controller and the diode. Therefore, the number of external components is reduced.

During system start-up, as long as the power converter has not operated normally (and has not produced an output voltage), the switch may be operated and the storage unit charged in accordance with the manner set forth above to power the controller IC. The proposed charging of the memory cell by means of a switch and a diode to supply current from the input port to the memory cell may be continued after the start-up is completed, e.g. during all operating times of the controller or the power converter.

The controller further comprises an (internal) resistor forming a voltage divider with an external resistor connected to the input port. The input voltage measurement unit may then be connected with the first terminal of the resistor to measure a portion of the input voltage determined by the voltage divider. The second terminal of the resistor may be connected to ground. For example, the portion of the input voltage applied at the first terminal of the resistor may be determined by the division ratio.

In many cases, the power converter includes a rectifier connectable to an Alternating Current (AC) mains supply, and the input voltage is the rectified mains voltage provided by the rectifier. The input voltage measurement unit may then determine a measurement value representing the input voltage, i.e. the rectified mains voltage. The determination may be periodic and the measurement may be the instantaneous voltage of the rectified mains voltage, which may be used to determine the current phase angle of the mains voltage, for example for detecting zero crossing of the mains voltage or application of a phase cut attenuator.

In order to control the supply voltage provided by the memory unit to the controller, the switch may be controlled in dependence on the amount of power stored on the memory unit, e.g. in dependence on the voltage of the capacitor. For example, the switch may be closed when the supply voltage provided by the capacitor reaches a predetermined voltage threshold, which may be higher than the normal supply voltage VCC. In the next period, the capacitor provides the power supply for the controller, and the supply current discharges the capacitor to drop the capacitor voltage. When the capacitor voltage drops below the second voltage threshold, the switch may be opened again to recharge the capacitor, and the charging cycle repeats.

In some embodiments, the input voltage measurement unit periodically samples the measured voltage to periodically determine a measured value of the input voltage. The sampling frequency may be higher than the mains frequency, preferably N times the mains frequency. Thus, the instantaneous voltage of the input voltage (mains voltage) can be measured N times during one mains cycle or mains half-cycle, and information on the current state of the input voltage, such as its phase, can be determined. This synchronizes the operation of e.g. the power converter with the mains cycle.

In some embodiments, the switch may be closed during a sampling time of the input voltage measurement unit. This may be advantageous to connect the input voltage measuring unit to the input port for measuring (dividing) the input voltage, especially when the input port is connected to the diode and the first terminal of the switch. This allows the input voltage measuring unit to sample the measured voltage at the second terminal of the switch.

In some embodiments, the controller further includes a current mirror coupled to the input port for receiving the current from the input port and dividing the current according to a current mirror ratio. In this case, a diode and a switch may be connected to a node of the first branch of the current mirror; and the input voltage measurement unit may be connected to a node of the second branch of the current mirror. The first branch thus carries a portion of the current received from the input port that can be used to charge the memory cell (via the diode), while the second branch carries a portion of the current that can be used to measure the input voltage. Thus, the current mirror may be configured such that the second branch carries only a small portion of the received current, but this is sufficient for measurement purposes.

As already mentioned above, the charging of the memory cell may be controlled by operating the switch, which in this embodiment is located in the first branch of the current mirror. For example, when the switch is open, the memory cell is charged, and when the switch is closed, for example when the voltage of the memory cell reaches a predefined voltage threshold, the charging is interrupted. The first branch of the current mirror further comprises for example a diode-connected transistor, a zener diode or a resistor connected between the second switch terminal and ground. These elements can limit the current flowing through the switch when the switch is closed and cause the voltage at the node of the first branch to be lower than the supply voltage VCC, thereby terminating the charging current flowing into the memory cell.

In some embodiments, the power converter is a switched mode power converter comprising at least one power switch; and the controller provides a drive signal to the at least one power switch to regulate the output voltage. For example, the converter may be a buck converter or a flyback converter as applied to an LED driver, where a mains power supply is converted and controlled to drive a series of solid state lighting elements to emit light.

According to another aspect, a method of powering a controller of a power converter that converts electrical power at an input voltage to electrical power at an output voltage is disclosed. The method includes receiving a voltage representative of an input voltage at an input port, sampling the measured voltage and determining a measured value representative of the input voltage, and controlling a switch to effect charging of a storage element, such as a capacitor, from the voltage at the input port, the capacitor providing a supply voltage to a controller during operation of the controller and being connected to a diode, which causes a charging current to flow from the input port to the capacitor.

The switch may be controlled in dependence of the supply voltage provided by the capacitor. To achieve this, the opening and closing of the switch is controlled to regulate the voltage at the capacitor so that the capacitor can be used as a regulated supply voltage for the controller to provide operating power for the controller throughout its operation. The switch may not only operate during start-up, but the amount of power stored in the capacitor may also power the controller IC after start-up, e.g. during the entire operation of the controller or power converter, as long as the power converter is not already operating properly. Preferably, therefore, no other means than the controller charges the capacitor, draws current from the input port with its switches and diodes, and provides the charging current to the capacitor.

The measurement voltage may be periodically sampled and a corresponding measurement of the input voltage may be generated. Between sampling periods, the switch may be opened to charge the capacitor without interrupting the measurement process.

The control of the switch may comprise controlling the time during which the switch is open or the switch remains closed between sampling periods in dependence on the supply voltage provided by the capacitor. For example, if the voltage at the capacitor is still high enough to be a supply voltage for a continuous time period, e.g. within a sampling/measurement period, there is no need to charge the capacitor and the charging cycle between successive sampling periods may be skipped, i.e. the switch is not opened during this time period. Alternatively, the charging time may be shortened if the capacitor voltage reaches a threshold value, indicating that there is sufficient charge in the capacitor to power the controller for a predetermined period of time.

The method also includes generating a drive signal for a power switch of the power converter and outputting the drive signal to the power switch. Thus, the controller may drive the switching power converter to power the output power supply at a desired output voltage.

It should be understood that the method steps and apparatus features may be interchanged in various ways. In particular, those skilled in the art may implement the details of the method disclosed as a means for performing some or all of the method steps, and vice versa. In particular, it should be understood that the methods disclosed herein relate to methods of operation of circuits according to the embodiments described above and their conversion, and that the various statements made in relation to such circuits apply equally to the corresponding methods.

Drawings

Embodiments of the invention are explained below by way of example with reference to the accompanying drawings, in which:

FIG. 1 schematically depicts an internal block diagram of a controller Integrated Circuit (IC) that controls the operation of a power converter, such as an LED driver; in particular, the controller IC may be used to drive one or more switches of a switched mode power converter;

FIG. 2 schematically depicts a portion of a controller IC according to the present invention; in particular, a switch is shown that can charge a capacitor; the capacitor can be used for charging a controller IC of the power converter; furthermore, an ADC converter is shown which can sample and measure the measurement voltage upon triggering of a control signal;

fig. 3 schematically shows a comparison of an input voltage VIN and an output voltage VCC depending on a switch activation state signal; fig. 3 furthermore shows the interaction between the switch activation state and the detection of the rail voltage performed by the ADC converter; and

FIG. 4 schematically illustrates another embodiment of the present invention; specifically, to charge the VCC supply and simultaneously measure the rail voltage, a current mirror is employed.

Detailed Description

The following examples of the present invention are explained in detail with reference to the accompanying drawings. Corresponding or substantially similar elements in the drawings have been denoted with the same reference numerals.

Fig. 1 schematically depicts a controller Integrated Circuit (IC)100 that controls the operation of a power converter, such as an LED driver. The controller 100 includes an input port VIN 203 for providing an input signal. In addition, a VIN to VCC charging path including a diode 206 is established between the VIN input port 203 and the VCC port 207. A capacitor 208 for driving the controller 100 is connected to the VCC port 207. In other words, the capacitor 208 provides a power supply for the controller integrated circuit 100. Further, the VCC-controller 101 is connected to the VIN-to-VCC charging path. The VCC controller 101 controls the activation and deactivation of a switch 209. the switch 209 is connected to the VIN to VCC charging path. The VCC controller 101 may control the activation state of the switch 209, as well as the charging process of the capacitor 208. The switch 209 is connected to the VIN to VCC charging path between the input port 203 of the controller 100 and the diode 206. The switch 209 is depicted as a MOSFET transistor, however, as described in detail below, the switch 209 may be in other forms. Specifically, the VCC controller 101 may measure the voltage of the capacitor 208, and may determine the opening and closing of the switch 209 based on the measured voltage, i.e., the amount of electricity stored in the capacitor 208. To open or close the switch 209, the VCC controller 101 may generate a signal SW that may control the switch state of the switch, i.e., control the switch to an open or closed state. Further, the IC100 receives operating power from a VIN-VCC charging path (not shown) connected to the VCC port 207.

Further, the switch 209 is connected to the resistor element 204 connected to the ground. A first input of multiplexer unit 102 is connected between switch 209 and resistor 204. A second input of the multiplexer unit 102 is connected to a further input port 103 of the controller 100, for example for receiving a temperature measurement signal V_T. The multiplexer unit 102 selects one of a plurality of input signals and transmits the selected input signal to an analog-to-digital converter (ADC) 205. The ADC205 is used to measure the rail voltage triggered by the control signal. The ADC205 provides an input to the attenuator detect and attenuator phase measurement unit 105. The attenuator detect and attenuator phase measurement unit 105 provides an input to a gate driver 106, the gate driver 106 being connected to an output port 107 and a resistor 106A. Adjacent to the attenuator detection and attenuator phase measurement unit 105 is a constant current control unit 108, which constant current control unit 108 provides an input to a gate driver 109. The gate driver 109 is connected to an output port 110 and a resistor 111. The output port of the gate driver may be connected to various switches for operating the power converter. The constant current control unit 108 is also connected to a signal conditioning unit 112. More specifically, the constant current control unit 108 receives a signal from the signal conditioning unit 112, the signal being related to an external input supplied to the signal conditioning unit 112 from the input port 113 of the controller 100. The input port 113 receives a signal V representing the output voltage of the power converter_SENSE. In addition, the constant current control unit 108 provides an input to a digital-to-analog converter 114.The output of the digital-to-analog converter 114 is provided as a conversion input to a comparator 115. The comparator 115 receives a non-inverting input from the input port 116 of the controller 100 and provides an output signal back to the constant current control unit 108. The input port 116 receives a signal I representing the output current of the power converter_SENSE. In addition, another comparator 116 compares the converted reference voltage with a non-inverting input received from the input port 116 and provides an output to the constant current control unit 108. The other port 117 of the controller 100 is connected to ground.

Fig. 2 discloses a part of a controller circuit for controlling a power converter, e.g. an LED driver. The principle of operation of measuring the mains voltage and supplying power to the controller 100 will be explained below in connection with the circuit shown in the figure.

Fig. 2 shows a full-wave rectifier 201, the full-wave rectifier 201 converting an Alternating Current (AC) to a Direct Current (DC). More precisely, full-wave rectification converts the two poles of an AC input waveform to pulsating DC. Various types of semiconductor diodes (junction diodes, schottky diodes, etc.) may be used for the power supply rectification process. Further, an external resistor 202 is connected between the input port 203 of the controller 100 and the full-wave rectifier 201. When combined, the structure of the outer resistor 202 and the inner resistor 204 may be connected to the input port 203 through a switch 209 and form a voltage divider. The internal resistor 204 is connected to ground. An input voltage measuring unit 205 is connected to the terminals of the internal resistor 204, so that the yi part of the mains voltage at the output of the rectifier can be measured. The voltage is determined in part by the voltage division ratio. The input voltage measurement unit 205 shown in fig. 2 is implemented by an analog-to-digital converter (ADC). The ADC205 is triggered to sample and measure a voltage based on receiving the control signal 205A.

In addition, a diode 206 is provided between the input port 203 of the controller 100 and the VCC port 207. The capacitor 208 is connected to the VCC port 207. Thus, diode 206 is located in the VIN-VCC charging path to capacitor 208. The diode 206 may prevent undesired current flow from the capacitor 208. Further, the above-described switch 209 is provided between the input port 203 of the controller 100 and the input voltage measurement unit 205. The switch 209 may be implemented as an electrically operated switch (relay) or a bilateral switch, i.e., an electronic component that behaves like an electrically operated switch but does not have moving parts (e.g., a MOSFET transistor as described above with respect to fig. 1).

The basic operating principle of the above circuit configuration will be described in detail below.

If the switch 209 is controlled to be in an open state, current from the rectifier 201 flows through the external resistor 202 and into the input port 203 of the controller 100. The current then flows through the diode 206 and into the capacitor 208, and charges the capacitor 208. Thus, the mains voltage may be used to provide a charging current to the capacitor 208 to drive the charging process. In other words, it is no longer necessary for the voltage generated by the external power supply or by the third winding of the flyback switching coil to charge the capacitor 208 and then to provide energy for the controller 100. Thus, the controller 100 can be supplied with electric power in a more efficient manner. Furthermore, even after a start-up phase (i.e., turn-on) of the controller 100, power supply may be achieved without the need for external power supply circuitry.

If the switch 209 is controlled to be closed, current from the rectifier 201 entering the controller 100 at the input port 203 flows through the closed switch 209 to ground via the internal resistor 204. As already mentioned above, the outer resistor 202 and the inner resistor 204 form a voltage divider or a potential divider. A voltage divider is a passive linear circuit that generates an output voltage that is a fraction of its input voltage. The resistor divider is used to generate a reference voltage or to reduce the magnitude of the voltage so that it can be measured. In particular, the ADC205 uses the voltage across the internal resistor 204 to determine a measurement value that is representative of the rail voltage. In this embodiment, the ADC205 is triggered to sample and measure the voltage at the measurement time point based on the receipt of the control signal 205A.

Since the mains power supply is an Alternating Current (AC) power supply and the input voltage is the rectified mains voltage provided by the rectifier 201, the measurement determined by the ADC205 is the instantaneous voltage of the rectified mains voltage. This information can therefore be used to determine the characteristics of the rail voltage. In particular, the current phase angle of the mains voltage may be determined by ACD 205 to determine a zero crossing of the input signal, or to control the second circuit using the determined characteristics. Furthermore, sampling the input signal at a fixed rate allows for an accurate reconstruction of the waveform, which allows for the LED drive switching circuit to be synchronized to the mains frequency.

Further, in the closed state of the switch 209, the discharge current of the capacitor 208 decreases the voltage of the capacitor. In particular, the switch 209 may be closed when the supply voltage of the capacitor 208 reaches a predetermined voltage threshold, which may be higher than the normal supply voltage VCC. The capacitor then provides the power supply to the controller 100 while being discharged by the supply current. When the voltage of the capacitor falls below a second predetermined threshold, the switch may be opened again, thereby recharging the capacitor through the VIN-VCC charging path. Thus, the number and duration of times the ADC performs the measurements corresponds to the charge-discharge cycles of the capacitor 208.

Fig. 3 schematically depicts a comparison of the time dependence of the input voltage VIN (curve 3) over time with the voltage at the VCC port 207 of the controller 100 (curve 4). The behavior of

curves

3 and 4 is described with respect to the activation mode SW _ R of switch 209 (curve 1) and the rail voltage period sampling signal CONV performed by ADC205 (curve 2). In other words, fig. 3 shows the dependence and time response of the voltages VIN and VCC with respect to the typical start-up state of the switch 209 as shown in fig. 2 and the rail voltage measurement of the ADC 205. This curve feature is discussed in detail in relation to the circuit shown in fig. 2.

As detailed in connection with fig. 2, to determine the rail voltage, the switch 209 is controlled to connect with the internal resistor 204 for a period of time. In the closed state of the switch 209, the current from the rectifier 201 flows through the internal resistor 204 to ground. During this time, the ADC205, as represented by the signal pulse 302 in CONV curve 2, can measure the rail voltage. The pulse 301 in the SW _ R curve 1 in fig. 3 represents the closed state of the switch 209.

Thus, in the closed state of the switch 209 (pulse 301 (high signal) in curve 1), the capacitor 208 is discharged by powering the controller. This is contrary toIs reflected in the variation of curve 4 of fig. 3, wherein the voltage level VCC decreases at the start of the switch 209, i.e. while the switch 209 is in the closed state. Meanwhile, as shown in curve 3, the voltage VIN at the input port 203 is at a constant level. At the same time, the ADC205 is enabled to supply the rail voltage V_MAINSThe measurement is performed. The measurement duration for which the ADC205 performs a mains voltage measurement is represented by the CONV pulse 302 in curve 2.

The switch 209 is open (represented by the low signal in curve 1) causing the capacitor 208 to charge by current flowing on the VIN-VCC charging path. Therefore, there is no voltage drop across the internal resistor 204, so that the ADC205 cannot achieve a voltage measurement as indicated by the low signal on curve 2.

On the other hand, after opening the switch 209, the current from the rectifier 201 charges the capacitor 208 and causes an increase in the capacitor voltage as indicated by the increased voltage VCC 304 in curve 4. At the same time, the voltage at the input port 203 increases corresponding to the voltage of the capacitor 208 as indicated by the voltage VIN 303 in curve 3. Thus, for V_MAINSThe switch 208 is controlled to be closed for voltage detection with the ADC, as measured. Controlling the switch 208 to a closed state may also stop the charging process of the capacitor 208. In other words, the switch 209 being actuated (closed) can effectively control the duration of the charging of the capacitor 208, and thus the magnitude of the VCC voltage. Thus, the mains voltage, which is only closely related to the process of the charge-discharge cycle of the capacitor 208, can be measured according to the embodiment shown in fig. 2.

Thus, the above arrangement cannot measure the mains voltage at any time, but relies on the switch 209 being actuated. This is also shown by a comparison of curve 1 and curve 2 in fig. 3, where V_MAINSThe voltage measurement event (pulse 302) occurs only for the duration of time that the capacitor 208 is not charged, i.e. when the switch 209 is in the closed state (pulse 301).

However, such interaction of switch actuation with the mains voltage measurement may enable simple control of the immediacy and/or duration of the mains voltage measurement by means of a control signal that governs the state of the switch 209.

Thus, the circuit configuration of this embodiment can sample the input rail voltage on a pulse width modulation basis of the input signal, thereby charging the VCC supply for the remaining time.

To allow VCC supply, i.e., charging of the capacitor 208, and simultaneously perform rail voltage measurement, the embodiment of the present invention as shown in fig. 4 employs a current mirror. More specifically, FIG. 4 depicts a circuit including a current mirror that can implement V_MAINSVoltage measurement and charging of the VCC power supply to drive the controller 100 independently of each other. The circuit shown in fig. 4 may be integrated into the controller 100 so that the controller 100 is operated in an alternating manner to provide operating power to the controller itself and to make mains voltage value measurements.

As discussed in previous embodiments of the present invention, a rectifier (not shown in FIG. 4) provides a voltage V_MAINS. An external resistor 202 is located between the rectifier and an input port 203 of the controller 100. Unlike the previous embodiment, a current mirror 210 is provided. The current mirror 210 may deviate the current from another reference current. In other words, the current mirror 210 may implement "replica" and "scaling" currents. The current mirror 210 thus represents a current driven current source.

More specifically, in the embodiment shown in fig. 4, the current mirror 210 is connected to the input port 203 and receives a current from the input port 203. The current mirror 210 includes a first branch 210A and a second branch 210B. The current mirror 210 may be configured such that the second branch 210B carries only a small portion of the received current. Thus, the current mirror 210 may divide the current according to a current mirror ratio determined by parameters of the first and

second branches

210A and 210B, and in particular determined by the size (geometry) of the transistor in the first branch 210A or the second branch 210B.

As further shown in fig. 4, a diode 206 and a switch 209 are connected to a node of a first branch 210A of a current mirror 210. The input voltage measurement unit, i.e., ADC205, is connected to a node of the second branch 210B of the current mirror 210. More specifically, two current paths extend from the node of the first leg 210A. The first current path includes a diode 206 and a VCC-port 207 that is connected to a power supply capacitor 208 and thus establishes the VIN-VCC charging path for capacitor 208.

A second current path extending from the first branch 210A of the current mirror 210 includes a switch 209 and a voltage setting circuit 211 connected to ground. The voltage setting circuit 211 in fig. 4 is depicted as a diode-connected transistor. However, a zener diode (which may be a variable or controllable zener diode) or a resistor may also be used, so that the voltage at the node of the first branch 210A may be lower than the supply voltage. This causes interruption of the charging current flowing into the capacitor 208 and prevents the capacitor 208 from being overcharged. Furthermore, cell 211 may define the current flowing through the second current path when switch 209 is closed. A second zener diode may be connected between the VIN-VCC charging path and ground (i.e., between diode 206 and VCC port 207; not shown) to limit the supply voltage VCC to a maximum value.

When the switch 209 is in the off state, current flows through the VIN-VCC charging circuit to the capacitor 208 and charges the capacitor 208. In addition, a scaled down version of the input current flows through current mirror leg 210B and through internal resistor 204 to ground, which allows ADC205 to perform mains voltage measurements.

Thus, even when the switch 209 is not activated, i.e. open, and the charging current is charging the capacitor 208, it is possible to perform a measurement of the mains voltage. In addition, to stop the charging process of the capacitor 208, the switch 209 may be controlled to activate as desired. Such activation of the switch 209 may result in an immediate interruption of the capacitor 208 charging current. Therefore, V can be performed without affecting ADC205_MAINSThe switch 209 is activated at the same time as the voltage measurement capability.

Thus, applications in which the supply voltage of the controller 100 is generated in dependence on the mains voltage and requires knowledge of the mains voltage waveform all benefit from the embodiment shown in figure 4 according to the invention. More specifically, the above-described embodiments of the present invention ensure that the power supply of the controller 100 is powered and that the mains voltage waveform can be measured simultaneously as desired. In other words, measuring the rail voltage may be performed independently of the charging process of the capacitor 208.

It should be noted that the description and drawings are only for the purpose of illustrating the principles of the proposed apparatus and method. It will thus be appreciated that those skilled in the art will be able to devise various arrangements which, although not explicitly described or shown herein, embody the principles of the invention and are thus within its spirit and scope. Furthermore, all examples set forth herein are principally intended to be exemplary and are intended to aid in understanding the principles of the methods and apparatus as well as the concepts claimed by the invention as they are extended by the prior art and are not intended to be limiting by the explicitly set forth examples or the environment. Furthermore, all statements herein reciting principles, aspects, and embodiments of the invention, as well as specific examples thereof, are intended to encompass equivalents thereof.

Claims

1. A controller for controlling a power converter to convert electrical power at an input voltage to electrical power at an output voltage, the controller comprising:

an input port for receiving a voltage representative of an input voltage;

an input voltage measurement unit for sampling a measured voltage and determining a measured value representative of the input voltage;

a switch;

a diode connected with the memory cell to provide a supply voltage to the controller during operation of the controller,

the input port is connected to the diode and a first terminal of the switch; the input voltage measuring unit samples the measured voltage at a second terminal of the switch;

wherein the second terminal of the switch is connected to one terminal of a resistor, and the other terminal of the resistor is connected to ground, an

A resistor forming a voltage divider with an external resistor connected to the input port; the input voltage measuring unit is connected with one terminal of the resistor and the second terminal of the switch to measure a part of the input voltage; the portion is determined by the partial pressure ratio;

wherein the switch is controlled to control charging of the storage cell from a voltage at the input port;

wherein the input voltage measurement unit periodically samples the measurement voltage to periodically determine a measurement value of the input voltage; and

the switch is closed during a sampling time of the input voltage measurement unit.

2. The controller of claim 1, wherein the power converter comprises a rectifier connected to an Alternating Current (AC) mains supply; the input voltage is a rectified mains voltage provided by the rectifier.

3. The controller of claim 1, wherein the switch is controlled according to a supply voltage provided by the storage unit.

4. The controller of claim 1, wherein the switch is closed when a supply voltage provided by the storage unit reaches a predefined voltage threshold.

5. A controller for controlling a power converter to convert electrical power at an input voltage to electrical power at an output voltage, the controller comprising:

an input port for receiving a voltage representative of an input voltage;

a switch; and

wherein the switch is controlled to control charging of the storage cell from a voltage at the input port, an

Wherein the input port is connected to the diode and a first terminal of the switch; the input voltage measuring unit samples the measured voltage at a second terminal of the switch;

wherein the second terminal of the switch is connected to one terminal of a resistor and the other terminal of the resistor is connected to ground; and

wherein the resistor and an external resistor connected to the input port form a voltage divider, and the input voltage measuring unit is connected with one terminal of the resistor and the second terminal of the switch to measure a portion of the input voltage, the portion being determined by a voltage dividing ratio.

6. The controller of claim 5, wherein the switch is controlled according to a supply voltage provided by the storage unit.

7. The controller of claim 5, wherein the switch is closed when a supply voltage provided by the storage unit reaches a predefined voltage threshold.